Metamaterials are artificial materials engineered to have properties that may not be found in nature. Metamaterials can gain their properties from structure rather than composition, using small inhomogeneities to create effective macroscopic behavior.
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization. Due to dielectric polarization, positive charges are displaced toward the field and negative charges shift in the opposite direction. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axis aligns to the field.
Magnetic permeability is the measure of the ability of a material to support the formation of a magnetic field within itself. Stated differently, the magnetic permeability of a material is the degree of magnetization that a material obtains in response to an applied magnetic field. The reciprocal of magnetic permeability is magnetic reluctivity.